Take your time! Even if your opponent plays very fast, you should still think carefully about every move you make.
Take notation! If you write down your game, you will be able to go over it with a coach. This way, you won’t make the same mistakes in the next tournament and will become a better player.
After your opponent makes his move, always try to figure out what she or he wants to do on the next move. Your opponent could be trying to capture your piece or checkmate you!
Get your pieces out as soon as you can and castle early!
Remember that chess pieces have different values! Make only the trades that are good for you (or at least even).